1. Field.
Example embodiments in general relate to a flange for joining a wind power generator to a pole structure, and more particularly to a flange for joining a wind power generator to a pre-stressed concrete tower, as well as to a flange for joining a heliostatic collector to a pre-stressed concrete tower.
2. Related Art
The increasing demand of energy from clean and non-contaminant sources has led to the development of off shore and inshore, wind power and heliostatic generators. Towers made of steel tube have been the typical solution to date. However, higher capacity multi-megawatt nacelles demand taller and stronger towers. Thus, pre-stressed concrete towers have been developed in an effort to handle these higher loads.
Where previously wind power generators of 2.75 MegaWatts (MW) and 3.6 MW of off-shore applications mounted on poles of 75 m were commonly used, increased sizes are now being seen; moving to wind power generators of 2 Giga Watts (GW) mounted in concrete pre-stressed towers of 110 m and taller. These concrete pre-stressed towers have a higher resistance to the wind and can better support the corrosion and nacelle weight when compared to the poles made of steel.
However, the connection of the concrete tower with the nacelle or a steel tube is done with a composite concrete-steel transition segment. Accordingly, performance problems can surface by the use of two different materials subjected to vibration and fatigue loads.
Intermediate bolted flange connections on steel towers have already been tested in the field for years. These flanges are usually mounted on the top of the concrete tower, welded to the upper end of the metallic reinforcing rods of the concrete pole or tower. The flange is under a high wind stress and can cause the rupture of the welded joints, damage to the concrete tower tip and consequent collapse of the nacelle.